Method for dividing substrate and method for manufacturing substrate using such method

ABSTRACT

Vertical cracks Vm in the thickness direction of a mother glass substrate 10 are sequentially formed along lines to be scribed and broken, and thus main scribe lines MS are formed along the lines to be scribed and broken of the mother glass substrate 10. Then, subordinate scribe lines SS are formed along the main scribe lines MS which have been formed, at a predetermined distance from the main scribe lines MS. Thus, the mother glass substrate 10 is broken along the main scribe lines MS. In this manner, the substrate can be scribed and broken efficiently without requiring a complicated device or the like.

TECHNICAL FIELD

The present invention relates to a substrate scribing and breakingmethod carried out for scribing and breaking a brittle materialsubstrate such as a glass substrate or the like used for a display panelsubstrate of a flat panel display (FPD) into a plurality of substrates.

BACKGROUND ART

Display panel substrates of liquid crystal display apparatuses or thelike are usually produced using glass substrates, which are brittlematerial substrates. A liquid crystal display apparatus is produced byassembling a pair of glass substrates with an appropriate gap interposedtherebetween and then enclosing a liquid crystal material in the gap.

For producing such a display panel substrate, an assembled mothersubstrate produced by assembling a pair of mother glass substrates isscribed and broken. Thus, a plurality of display panel substrates areproduced from the assembled mother substrate. A substrate scribing andbreaking method used for scribing and breaking an assembled mothersubstrate is disclosed in Japanese Laid-Open Publication No. H6-48755(patent document 1).

FIGS. 15A through 15D show steps of scribing and breaking a mothersubstrate described above. In the following description, for the sake ofsimplicity, among a pair of mother glass substrates facing each otherwhich are assembled together to produce an assembled mother glasssubstrate, one mother glass substrate will be referred to as the “A sideglass substrate” and the other will be referred to as the “B side glasssubstrate”.

(1) First, as shown in FIG. 15A, an assembled mother substrate 901 isplaced on a first scribing device with an A side glass substrate of theassembled mother substrate 901 as an upper substrate. Using a cutterwheel 902, a scribe line Sa is formed in the A side glass substrate.

(2) Next, the assembled mother substrate 901 with the scribe line Saformed in the A side glass substrate is inverted, and the assembledmother substrate 901 is transported to a first breaking device. In thefirst breaking device, as shown in FIG. 15B, the assembled mothersubstrate 901 is placed on a mat 904. A break bar 903 is pressed on theB side glass substrate of the assembled mother substrate 901 along thescribe line Sa formed in the A side glass substrate. By this operation,a vertical crack extends upward from the scribe line Sa in the A sideglass substrate which is placed as a lower substrate, and the A sideglass substrate is broken along the scribe line Sa.

(3) Next, the assembled mother substrate 901 with the A side glasssubstrate being broken is transported to a second scribing devicewithout inverting the assembled mother substrate 901. In the secondscribing device, as shown in FIG. 15C, a surface of the B side glasssubstrate of the assembled mother substrate 901 is scribed using thecutter wheel 902, and thus a scribe line Sb is formed parallel to thescribe line Sa. The scribe line Sb formed in the B side glass substrateis often formed offset in the horizontal direction from the scribe lineSa formed in the A side glass substrate. The reason is that theassembled mother substrate 901 has a plurality of display panel areasand an electrode terminal portion needs to be formed on a peripheralportion of one of the glass substrates of the display panel substrate.

(4) Then, the assembled mother substrate 901 is inverted to put the Aside glass substrate as the upper substrate, and is transported to asecond breaking device. In the second breaking device, as shown in FIG.15D, the assembled mother substrate 901 is placed on the mat 904. Abreak bar 903 is pressed on the A side glass substrate, at a portioncorresponding to the scribe line Sb formed in the B side glasssubstrate, along the scribe line Sb. By this operation, the B side glasssubstrate as the lower substrate is broken along the scribe line Sb.

By performing the above steps (1) through (4), the assembled mothersubstrate 901 is scribed and broken at a desired position.

The above-described substrate scribing and breaking method requires aninversion step for inverting the assembled mother substrate in order toscribe and break one of the mother glass substrates of the assembledmother substrate, and a breaking step of breaking the one mother glasssubstrate by extending a vertical crack formed by scribing the onemother glass substrate. There is a problem that a substrate scribing andbreaking device for performing these steps requires a complicatedstructure and a large area for installment.

The above-described substrate scribing and breaking method also has aproblem that a demand for reducing the production cost of display panelscannot be fully met.

A method used in a conventional breaking step, i.e., a method ofpressing a rear surface of a substrate along a scribe line to scribe andbreak the substrate, has a problem that an edge of a broken surface ofthe substrate is, for example, easily chiseled off.

The present invention, for solving these problems, has an objective ofproviding a method for scribing and breaking a substrate efficientlywithout requiring a complicated device.

DISCLOSURE OF THE INVENTION

According to the present invention, a substrate scribing and breakingmethod is provided, which includes the steps of forming a main scribeline along a line to be scribed and broken of a brittle substrate; andforming a subordinate scribe line immediately close to, andsubstantially parallel to, the main scribe line which has been formed;wherein the substrate is broken along the main scribe line by theformation of the subordinate scribe line.

Namely, a vertical crack having a surface of the substrate as a baseportion is formed along the line to be scribed and broken by theformation of the main scribe line; a compressive force is generated on asurface portion of the vertical crack by the formation of thesubordinate scribe line, thereby generating a tensile force on a bottomportion of the substrate; and the vertical crack can extend to thebottom portion of the substrate to break the substrate.

According to a conventional method, a vertical crack having a surface ofthe substrate as a base portion is formed along the line to be scribedand broken by the formation of the scribe line; a substrate inversiondevice is used to invert the substrate; then, a breaking device is usedto break the substrate from a rear surface of the substrate to generatea compressive force on the substrate surface portion of the verticalcrack, thereby generating a tensile force on a bottom portion of thesubstrate; and the vertical crack extends to the bottom portion of thesubstrate to break the substrate. According to the substrate subscribingand breaking method of the present invention, the substrate can bebroken by forming a subordinate scribe line on the surface of thesubstrate on which a main scribe line has been formed, without invertingthe substrate and breaking the substrate from the rear surface thereofas conventionally required.

As a result, the substrate inversion device and the breaking device arenot necessary, and therefore the structure can be simplified and theinstallment area can be reduced.

The substrate scribing and breaking method is characterized in that thesubordinate scribe line is formed at a distance of 0.5 mm to 1 mm fromthe main scribe line.

The substrate scribing and breaking method is characterized in that themain scribe line is formed of a vertical crack extending over at least80% of the thickness direction of the substrate from the surface of thesubstrate.

More preferably, the substrate scribing and breaking method ischaracterized in that the main scribe line is formed of a vertical crackextending over at least 90% of the thickness direction of the substratefrom the surface of the substrate.

The main scribe line is formed by a disc-shaped cutter wheel which rollson the surface of the substrate; a central portion of an outercircumferential surface of the cutter wheel in a thickness directionthereof projects outward to form a V-shape of an obtuse angle; and aplurality of protrusions having a predetermined height are provided atthe obtuse angled portion along the entire circumference at apredetermined pitch. Thus, a vertical crack extending over at least 80%of the thickness direction of the substrate from the surface of thesubstrate can be easily formed.

A forming direction of the main scribe line and a forming direction ofthe subordinate scribe line by the cutter wheel are opposite to eachother; and the cutter wheel forms the main scribe line and thesubordinate scribe line continuously in the state of being in contactwith the surface of the substrate. Thus, the distance by which thecutter wheel moves from a formation end position of the main scribe lineto a formation start position of the subordinate scribe line can beshortened. In addition, the cutter wheel can be easily positioned to theformation start position of the subordinate scribe line.

Either the main scribe line or the subordinate scribe line is formedsuch that a start position or an end position thereof is an appropriatedistance away from at least one end of the line to be scribed andbroken. Thus, an end portion of the substrate can be prevented frombeing chiseled off.

Preferably, the substrate scribing and breaking method is characterizedin that after at least two main scribe lines are formed by a cutterwheel tip along at least two continuous lines to be scribed and brokenof the substrate, subordinate scribe lines which are substantiallyparallel to the at least two main scribe lines which have been formedare formed by the cutter wheel tip.

Preferably, the substrate scribing and breaking method is characterizedin that the main scribe lines are formed continuously without separatingthe cutter wheel tip from the surface of the substrate.

Preferably, the substrate scribing and breaking method is characterizedin that the subordinate scribe lines are formed continuously withoutseparating the cutter wheel tip from the surface of the substrate.

Preferably, the substrate scribing and breaking method is characterizedin that the cutter wheel tip forms one of the scribe lines, then moveson the substrate so as to draw a circular line, and then forms the otherof the scribe lines.

Preferably, the substrate scribing and breaking method is characterizedin that while the cutter wheel tip moves on the substrate so as to drawa circular line, a pressure acting on the substrate is lower than apressure acting on the substrate when each of the scribe lines isformed.

According to another aspect of the present invention, a panel productionmethod for scribing and breaking a brittle substrate to produce aplurality of quadrangular panels which are continuous in at least onedirection is provided. The method includes the steps of setting fourlines to be scribed and broken for the four-sided panels on thesubstrate; forming scribe lines along two lines to be scribed and brokenfacing each other which have been set; and then forming scribe linesalong the remaining two lines to be scribed and broken facing each otherwhich have been set; wherein the scribe lines along the remaining twolines to be scribed and broken are formed so as to cross the scribelines along the two lines to be scribed and broken first formed, therebybreaking the substrate along the scribe lines to produce thequadrangular panels.

Namely, when the scribe lines later formed cross the two scribe linesfirst formed, a force for pushing wide the vertical crack forming thescribe lines first formed is generated. By this force, the substrate isbroken along the scribe lines.

Accordingly, the substrate can be broken by forming the subordinatescribe lines on the surface of the substrate on which the main scribelines have been formed, without inverting the substrate and breaking thesubstrate from the rear surface thereof as conventionally required.

As a result, the substrate inversion device and the breaking device arenot necessary, and therefore the structure can be simplified and theinstallment area can be reduced.

According to another aspect of the present invention, a panel productionmethod for scribing and breaking a brittle substrate to produce aplurality of quadrangular panels continuous in at least one direction isprovided. The method includes the steps of setting four lines to bescribed and broken for the four-sided panels on the substrate; formingmain scribe lines along the four lines to be scribed and broken whichhave been set; and forming subordinate scribe lines immediately closeto, and substantially parallel to, the main scribe lines which have beenformed; wherein the substrate is broken along the main scribe lines bythe formation of the subordinate scribe lines to produce thequadrangular panels.

The scribe lines are formed along the four lines to be scribed andbroken which have been formed for the panels. Thus, the substrate can bebroken by forming the subordinate scribe lines on the surface of thesubstrate on which the main scribe lines have been formed, withoutinverting the substrate and breaking the substrate from the rear surfacethereof as conventionally required.

As a result, the substrate inversion device and the breaking device arenot necessary, and therefore the structure can be simplified and theinstallment area can be reduced.

A scribe line is formed along at least one of the remaining two lines tobe scribed and broken facing each other, using a substrate scribing andbreaking method according to the present invention. Thus, the substratecan be broken by forming the subordinate scribe lines on the surface ofthe substrate on which the main scribe lines have been formed, withoutinverting the substrate and breaking the substrate from the rear surfacethereof as conventionally required.

As a result, the substrate inversion device and the breaking device arenot necessary, and therefore the structure can be simplified and theinstallment area can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a substrate illustrating theprinciple of a substrate scribing and breaking method according to thepresent invention.

FIG. 2A is a front view of a cutter wheel used for carrying out thesubstrate scribing and breaking method according to the presentinvention, FIG. 2B is a side view thereof, and FIG. 2C is a partialenlarged view of FIG. 2B.

FIG. 3 is a plan view of a mother glass substrate illustrating asubstrate scribing and breaking method according to the presentinvention.

FIG. 4 is a partial plan view of a mother glass substrate illustratinganother substrate scribing and breaking method according to the presentinvention.

FIGS. 5A and 5B are plan views of a mother glass substrate illustratingstill another substrate scribing and breaking method according to thepresent invention.

FIG. 6 is a partial plan view of a mother glass substrate illustratingstill another substrate scribing and breaking method according to thepresent invention.

FIG. 7 is a plan view of a mother glass substrate illustrating stillanother substrate scribing and breaking method according to the presentinvention.

FIG. 8 is a plan view of a mother glass substrate illustrating stillanother substrate scribing and breaking method according to the presentinvention.

FIG. 9 is a plan view of a mother glass substrate illustrating ascribing method used for the substrate scribing and breaking method ofthe present invention shown in FIG. 8.

FIG. 10 is a plan view of a mother glass substrate illustrating stillanother substrate scribing and breaking method according to the presentinvention.

FIG. 11 is a plan view of a mother glass substrate illustrating stillanother substrate scribing and breaking method according to the presentinvention.

FIG. 12 is a schematic perspective view of a display panel substrateformed by applying a substrate scribing and breaking method according tothe present invention.

FIG. 13 is a plan view illustrating a structure of an assembled mothersubstrate used for producing the liquid crystal display panel substrateshown in FIG. 12.

FIG. 14 is a bottom view illustrating a structure of an assembled mothersubstrate used for producing the liquid crystal display panel substrateshown in FIG. 12.

FIGS. 15A through 15D show steps of a conventional substrate scribingand breaking method.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described by way of exampleswith reference to the drawings.

First, the principle of a substrate scribing and breaking methodaccording to the present invention will be described. The substratescribing and breaking method according to the present invention iscarried out for, for example, scribing and breaking a single motherglass substrate to obtain a plurality of glass substrates. According tothe substrate scribing and breaking method of the present invention, asshown in FIG. 1, a cutter wheel 20, for example, is pressure-contactedand rolled on a mother glass substrate 10 along a line to be scribed andbroken of the mother glass substrate 10 (along which the mother glasssubstrate 10 will be scribed and broken). Thus, the mother glasssubstrate 10 is scribed. By this operation, a vertical crack Vm in thethickness direction of the mother glass substrate 10 is sequentiallyformed along the line to be scribed and broken. Thus, a main scribe lineMS is formed. The vertical crack Vm is formed so as to extend over 80%or more, more preferably 90% or more, of the thickness of the motherglass substrate 10 from a surface of the mother glass substrate 10.

Then, outside an area of a glass substrate obtained by scribing andbreaking the mother glass substrate 10, the cutter wheel 20 ispressure-contacted and rolled on the mother glass substrate 10substantially parallel to the main scribe line MS at a distance of about0.5 mm to 1 mm from the main scribe line MS. Thus, the mother glasssubstrate 10 is scribed. By this operation, a vertical crack Vs in thethickness direction of the mother glass substrate 10 is sequentiallyformed on the main scribe line MS. Thus, a subordinate scribe line SS isformed.

When the subordinate scribe line SS is formed, the cutter wheel 20 ispressure-contacted and rolled on the surface of the mother glasssubstrate 10 and thus a blade of the cutter wheel 20 eats into thesurface of the mother glass substrate 10. Therefore, a surface portionof the mother glass substrate 10 is subjected to a compressive force,which acts on a surface portion of the vertical crack Vm forming themain scribe line MS already formed. The vertical crack Vm forming themain scribe line MS extends over 80% or more of the thickness of themother glass substrate 10. Since the surface portion of the mother glasssubstrate 10 is compressed, the opening of the vertical crack Vm(forming the main scribe line MS) in the surface portion of the motherglass substrate 10 is compressed and the vertical crack Vm is pulledtoward a bottom surface of the mother glass substrate 10. Therefore, thevertical crack Vm extends toward, and reaches, the bottom surface of themother glass substrate 10. The vertical crack Vm reaches the bottomsurface of the mother glass substrate 10 over the entire length of themain scribe line MS. As a result, the mother glass substrate 10 isbroken along the main scribe line MS.

The subordinate scribe line SS is preferably formed at a distance ofabout 0.5 mm to 1 mm from the main scribe line MS. When the subordinatescribe line SS is formed at a distance of less than 0.5 mm from the mainscribe line MS, an excessively large compressive force acts on thesurface portion of the vertical crack Vm forming the main scribe lineMS, which may undesirably result in a damage such as a chiseled-off orthe like at an end of the vertical crack Vm on the surface of the motherglass substrate 10. When the subordinate scribe line SS is formed at adistance of more than 1.0 mm from the main scribe line MS, thecompressive force acting on the surface portion of the vertical crack Vmforming the main scribe line MS is insufficient, which may undesirablyresult in the vertical crack Vm not reaching the bottom surface of themother glass substrate 10.

FIG. 2A is a front view of the cutter wheel 20 disclosed in JapaneseLaid-Open Publication No. H9-188534 as used for such a substratescribing and breaking method. FIG. 2B is a side view thereof, and FIG.2C is a partial enlarged view thereof. The cutter wheel 20 isdisc-shaped and has a diameter of φ and a thickness of W. An outercircumferential surface is V-shaped with the center of the thickness Wdirection projecting outward. A tip of the projection forms a bladeportion having an obtuse angle α. The blade portion has a plurality ofprotrusions 21 formed along the entire circumference at a predeterminedpitch p. The protrusions 21 have a predetermined height h. Each of theprotrusions 21 has a micron-order size and cannot be actually viewed bynaked eye.

The cutter wheel 20 having such a structure has a very high capabilityof forming a vertical crack. As described above, a deep vertical crack11 a extending over about 90% of the thickness of the mother glasssubstrate 10 from the surface thereof can be formed by scribing themother glass substrate 10 using the cutter wheel 20. Accordingly, themother glass substrate 10 can be broken with certainty by carrying outthe substrate scribing and breaking method according to the presentinvention using the cutter wheel 20.

The substrate scribing and breaking method according to the presentinvention is not limited to using the cutter wheel 20. Any means isusable as long as a vertical crack forming the main scribe line extendsover about 80% or more of the thickness of the substrate from thesurface of the substrate. For example, a scribing device for vibrating ascribe cutter using a vibrator (piezoelectric device) to form a verticalcrack in a substrate is usable.

The formation direction of the main scribe line MS and the formationdirection of the subordinate scribe line SS may be opposite to eachother. In this case, while the cutter wheel 20 is in contact with thesurface of the mother glass substrate 10 from a formation end positionof the main scribe line MS to a formation start position of thesubordinate scribe line SS, the scribe direction is inverted. In thisembodiment, the moving distance of the cutter wheel 20 from theformation end position of the main scribe line MS to the formation startposition of the subordinate scribe line SS can be shortened, and inaddition, the cutter wheel 20 can be easily placed at the formationstart position of the subordinate scribe line SS. Therefore, the motherglass substrate 10 can be efficiently broken.

Next, a practical example of a method for scribing and breaking glasssubstrates from a mother glass substrate using the substrate scribingand breaking method according to the present invention will bedescribed. In the following description, a mother glass substrate isbroken without being assembled with another mother glass substrate. Thepresent invention is not limited to this, and is applicable to the casewhere each of a pair of mother glass substrates assembled together isbroken.

FIG. 3 is a plan view illustrating a scribe pattern for scribing andbreaking glass substrates 10 a from the mother glass substrate 10 usingdouble scribe lines, i.e., the main scribe line MS and the subordinatescribe line SS. In this example, the mother glass substrate 10 isscribed and broken along first through eighth lines to be scribed andbroken D1 through D8 in this order. As a result, four glass substrates10 a (two rows×two columns) are obtained.

The first line to be scribed and broken D1 corresponds to arow-direction (lateral-direction) edge of the two glass substrates 10 ain the first row. The first line to be scribed and broken D1 is at apredetermined distance from one row-direction edge of the mother glasssubstrate 10. The second line to be scribed and broken D2 corresponds toa row-direction edge of the two glass substrates 10 a in the first row,the row-direction edge being close to the glass substrates 10 a in thesecond row. The third line to be scribed and broken D3 corresponds to arow-direction edge of the two glass substrates 10 a in the second row,the row-direction edge being close to the glass substrates 10 a in thefirst row. The third line to be scribed and broken D3 is at a distanceof 2 mm to 4 mm from the second line to be scribed and broken D2. Thefourth line to be scribed and broken D4 corresponds to a row-direction(lateral-direction) edge of the two glass substrates 10 a in the secondrow. The fourth line to be scribed and broken D4 is at a predetermineddistance from the other row-direction edge of the mother glass substrate10.

The fifth line to be scribed and broken DS corresponds to acolumn-direction (perpendicular-direction) edge of the two glasssubstrates 10 a in the first column. The fifth line to be scribed andbroken D5 is at a predetermined distance from one column-direction edgeof the mother glass substrate 10. The sixth line to be scribed andbroken D6 corresponds to a column-direction edge of the two glasssubstrates 10 a in the first column, the column-direction edge beingclose to the glass substrates 10 a in the second column. The seventhline to be scribed and broken D7 corresponds to a column-direction edgeof the two glass substrates 10 a in the second column, thecolumn-direction edge being close to the glass substrates 10 a in thefirst column. The seventh line to be scribed and broken D7 is at adistance of 2 mm to 4 mm from the sixth line to be scribed and brokenD6. The eighth line to be scribed and broken D8 corresponds to acolumn-direction (perpendicular-direction) edge of the two glasssubstrates 10 a in the second column. The eighth line to be scribed andbroken D8 is at a predetermined distance from the other column-directionedge of the mother glass substrate 10.

The mother glass substrate 10 is scribed and broken as follows. Thecutter wheel 20, for example, is first rolled while in pressure contactwith the mother glass substrate 10 along the first through fourth linesto be scribed and broken D1 through D4 in this order. By this operation,a vertical crack having a depth of 90% or more of the thickness of themother glass substrate 10 is formed immediately below first throughfourth main scribe lines MS1 through MS4.

In this example, the phenomenon that the vertical crack generated by theformation of a scribe line advances in a direction parallel to thesurface of the mother glass substrate 10 will be referred to as“proceed”. The phenomenon that the vertical crack generated by theformation of a scribe line advances in a direction perpendicular to thesurface of the mother glass substrate 10 will be referred to as“extension”.

Once the above-described state is obtained, the cutter wheel 20 isrolled in pressure contact with the mother glass substrate 10 along thefifth line to be scribed and broken D5. By this operation, a fifth mainscribe line MS5 is formed along the fifth line to be scribed and brokenD5.

After this the cutter wheel 20 is rolled in pressure contact with themother glass substrate 10 along the sixth through eighth lines to bescribed and broken D6 through D8 in this order. Thus, sixth througheighth main scribe lines MS6 through MS8 are formed along the sixththrough eighth lines to be scribed and broken D6 through D8 in thisorder.

After the first through eighth main scribe lines MS1 through MS8 areformed in this manner, the cutter wheel 20 is rolled in pressure contactwith the mother glass substrate 10 along a line parallel to the edge ofthe mother glass substrate 10. The line is on the opposite side to theglass substrates 10 a in the first row with respect to the first mainscribe line MS1 and is at a distance of about 0.5 mm to 1 mm from thefirst main scribe line MS1. Thus, a first subordinate scribe line SS1 isformed along the first main scribe line MS1. By this operation, avertical crack forming the first main scribe line MS1 extends toward,and reaches, the bottom surface of the mother glass substrate 10. Bythis action occurring along the entirety of the first main scribe lineMS1, the mother glass substrate 10 is broken along the first main scribeline MS1.

Next, a second subordinate scribe line SS2 is formed using the cutterwheel 20. The second subordinate scribe line SS2 is parallel to thesecond main scribe line MS2, is on the opposite side to the glasssubstrates 10 a in the first row with respect to the second main scribeline MS2, and is at a distance of about 0.5 mm to 1 mm from the secondmain scribe line MS2. By this operation, a vertical crack forming thesecond main scribe line MS2 extends toward, and reaches, the bottomsurface of the mother glass substrate 10. By this action occurring alongthe entirety of the second main scribe line MS2, the mother glasssubstrate 10 is broken along the second main scribe line MS2.

A third subordinate scribe line SS3 and a fourth subordinate scribe lineSS4 are formed respectively along the third main scribe line MS3 and thefourth main scribe line MS4, on the opposite side to the glasssubstrates 10 a in the second row with respect to the third main scribeline MS3 and the fourth main scribe line MS4. Then, the mother glasssubstrate 10 is broken along the third main scribe line MS3 and thefourth main scribe line MS4.

Then, fifth through eighth subordinate scribe lines SS5 through SS8 areformed along the fifth through eighth main scribe lines MS5 through MS8between the first main scribe line MS1 and the second main scribe lineMS2 and between the third main scribe line MS3 and the fourth mainscribe line MS4, respectively. The fifth through eighth subordinatescribe lines SS5 through SS8 are respectively formed on the oppositesides to the glass substrates 10 a in the first column and in the secondcolumn with respect to the fifth through eighth main scribe lines MS5through MS8. By this operation, the mother glass substrate 10 is brokenalong the fifth through eighth main scribe lines MS5 through MS8.Unnecessary portions are removed, and the four glass substrates 10 a areobtained.

In this case, the first through eighth main scribe lines MS1 through MS8are formed along the entirety of the lines to be scribed and broken D1through D8 which are formed between opposing end surfaces of the motherglass substrate 10. The first through eighth subordinate scribe linesSS1 through SS8 are formed between opposing end surfaces or opposingbroken surfaces of the mother glass substrate 10.

The present invention is not limited to forming the first through eighthmain scribe lines MS1 through MS8 along the entirety of the lines to bescribed and broken D1 through D8 which are formed between opposing endsurfaces of the mother glass substrate 10 and forming the first througheighth subordinate scribe lines SS1 through SS8 between opposing endsurfaces or opposing broken surfaces of the mother glass substrate 10.

The following method shown in FIG. 4 is also usable. A position at anappropriate distance of about 0.2 mm to 0.5 mm from one end surface ofthe mother glass substrate 10 is set as a start point of each of firstthrough eighth main scribe lines MS1 through MS8. Similarly, a positionat an appropriate distance of about 0.2 mm to 0.5 mm from the other endsurface of the mother glass substrate 10 is set as an end point of eachof the first through eighth main scribe lines MS1 through MS8.

In this case, when the cutter wheel 20 is rolled in pressure contactwith the mother glass substrate 10 to scribe the mother glass substrate10, a vertical crack proceeds in forward and backward directions fromthe scribe start position. Therefore, the first through eighth mainscribe lines MS1 through MS8 each reach one end surface of the motherglass substrate 10.

Similarly, even through the scribe end position of each of the firstthrough eighth main scribe lines MS1 through MS8 is at a distance fromthe other end surface of the mother glass substrate 10, the verticalcrack proceeds in the scribe direction. Therefore, the first througheighth main scribe lines MS1 through MS8 each reach the other endsurface of the mother glass substrate 10.

Based on this, it is not necessary to form each of first through eighthsubordinate scribe line SS1 through SS8 from one end surface to theother end surface, or from one broken surface to the other brokensurface, of the mother glass substrate 10. According to the method shownin FIG. 4, a position at an appropriate distance of about 0.2 mm to 0.5mm from one end surface or one broken surface of the mother glasssubstrate 10 is set as a start point of each of the first through eighthsubordinate scribe lines SS1 through SS8. Similarly, a position at anappropriate distance of about 0.2 mm to 0.5 mm from the other endsurface or the other broken surface of the mother glass substrate 10 isset as an end point of each of the first through eighth subordinatescribe lines SS1 through SS8.

Alternatively, the following method is usable. One of (i) first througheighth main scribe lines MS1 through HS8 and (ii) first through eighthsubordinate scribe lines SS1 through SS8 are each formed from one endsurface or one broken surface of the mother glass substrate 10 to theother end surface or the other broken surface of the mother glasssubstrate 10. The other of (i) the first through eighth main scribelines MS1 through MS8 and (ii) the first through eighth subordinatescribe lines SS1 through SS8 are each formed from a position which is atan appropriate distance from one end surface or one broken surface ofthe mother glass substrate 10 to a position which is at an appropriatedistance from the other end surface or the other broken surface of themother glass substrate 10.

FIGS. 5A and 5B are plan views illustrating another scribe pattern forscribing and breaking glass substrates 10 a from the mother glasssubstrate 10. According to this scribing method, first and second mainscribe lines MS1 and MS2 are formed along first and second lines to bescribed and broken D1 and D2 in a lateral direction of the mother glasssubstrate 10, using the cutter wheel 20. A vertical crack forming eachof the first and second main scribe lines MS1 and MS2 extends over 90%or more of the thickness of the mother glass substrate 10 from thesurface thereof. Then, a fifth main scribe line MS5 is formed in an areabetween the first main scribe line MS1 and the second main scribe lineMS2, along a fifth line to be scribed and broken D5 in a perpendiculardirection (perpendicular to the lateral direction), using the cutterwheel 20. After this, a fifth subordinate scribe line SS5 is formed at adistance of about 0.5 mm to 1 mm from the fifth main scribe line MS5, onthe opposite side from the glass substrate 10 a with respect to thefifth main scribe line MS5.

In this case, the fifth main scribe line MS5 and the fifth subordinatescribe line SS5 cross the first and second main scribe lines MS1 and MS2already formed. After the fifth main scribe line MS5 crosses the secondmain scribe line MS2, the cutter wheel 20 is rotated at 180 degrees toform the fifth subordinate scribe line SS5. In this manner, the fifthmain scribe line MS5 and the fifth subordinate scribe line SS5 can becontinuously formed in one scribe operation.

After this, similarly, a sixth main scribe line MS6 is formed in an areabetween the first main scribe line MS1 and the second main scribe lineMS2, along a sixth line to be scribed and broken D6, using the cutterwheel 20. The cutter wheel 20 is rotated at 180 degrees to form thesixth subordinate scribe line SS6 on the opposite side from the glasssubstrate 10 a with respect to the sixth main scribe line MS6. Then, aseventh main scribe line MS7 and a seventh subordinate scribe line SS7,and an eighth main scribe line MS8 and an eighth subordinate scribe lineSS8 are sequentially formed in a similar manner. Since the fifth througheighth main scribe lines MS5 through MS8 and the fifth through eighthsubordinate scribe lines SS5 through SS8 pass the first and second mainscribe lines MS1 and MS2, a vertical crack forming each of the first andsecond main scribe lines MS1 and MS2 reaches the bottom surface of themother glass substrate 10 with certainty over the entirety of the firstand second main scribe lines MS1 and MS2. Therefore, the mother glasssubstrate 10 is broken along the first and second main scribe lines MS1and MS2 with certainty, and thus a pair of glass substrates 10 a areobtained.

An area of the mother glass substrate 10 which has not been scribed andbroken is referred to as a second substrate area 10 c.

Next, as shown in FIG. 5B, the cutter wheel 20 is rolled in pressurecontact with the mother glass substrate 10 in the second substrate area10 c obtained by the second main scribe line MS2. Thus, third and fourthmain scribe lines MS3 and MS4 are formed along third and fourth lines tobe scribed and broken D3 and D4 in the lateral direction of the motherglass substrate 10. A vertical crack forming each of the third andfourth main scribe lines MS3 and MS4 extends over 90% or more of thethickness of the mother glass substrate 10 from the surface thereof.Then, in an area between the third main scribe line MS3 and the fourthmain scribe line MS4, the following scribe lines are formed sequentiallyin the perpendicular direction so as to cross the third and fourthscribe lines MS3 and MS4: a ninth main scribe line MS5 along a ninthline to be scribed and broken D9 and a ninth subordinate scribe lineSS9, a tenth main scribe line MS10 along a tenth line to be scribed andbroken D10 and a tenth subordinate scribe line SS10, an eleventh mainscribe line MS11 along an eleventh line to be scribed and broken D11 andan eleventh subordinate scribe line SS11, and a twelfth main scribe lineMS12 along a twelfth line to be scribed and broken D12 and a twelfthsubordinate scribe line SS12. The ninth subordinate scribe line SS9, thetenth subordinate scribe line SS10, the eleventh subordinate scribe lineSS11, and the twelfth subordinate scribe line SS12 are formed outsidethe corresponding glass substrates 10 a. In this manner, the secondsubstrate area 10 c is broken, and thus a pair of glass substrates 10 aare obtained.

The fifth through twelfth subordinate scribe lines SS5 through SS12 donot need to cross the first and the third main scribe lines MS1 and MS3,respectively. For example, as shown in FIG. 6, a position which is about0.2 mm to 0.5 mm before each of the first main scribe line MS1 and thethird main scribe line MS3 may be set as an end position of each of thefifth through twelfth subordinate scribe lines SS5 through SS12. In thiscase also, a vertical crack forming each of the fifth through twelfthsubordinate scribe lines SS5 through SS12 proceeds in the scribedirection. The mother glass substrate 10 is broken along the entirety ofthe fifth through twelfth main scribe lines MS5 through MS12.

For breaking themother glass substrate 10 bycrossing scribe lines eachother, the method shown in FIG. 7 is also usable. First through fourthmain scribe lines MS1 through MS4 are formed in the mother glasssubstrate 10 along first through fourth lines to be scribed and brokenD1 through D4. Thereafter, a fifth main scribe line MS5 and a fifthsubordinate scribe line SS5, a sixth main scribe line MS6 and a sixthsubordinate scribe line SS6, a seventh main scribe line MS7 and aseventh subordinate scribe line SS7, and an eighth main scribe line MS8and an eighth subordinate scribe line SS8 are formed. The cutter wheel20 is rotated at 180 degrees after each main scribe line crosses thefourth main scribe line MS4 to form the respective subordinate scribeline. In this way, each pair of main scribe line and subordinate scribeline can be formed continuously by one scribe operation.

FIGS. 8 through 10 are schematic plan views illustrating still anotherscribe pattern for scribing and breaking glass substrates 10 a from themother glass substrate 10 using the double scribe lines, i.e., a mainscribe line MS and a subordinate scribe line SS. First, as shown inFIGS. 8 and 9, four scribe lines along lines to be scribed and broken S1through S4 surrounding a glass substrate 10 a are formed. (Hereinafter,the four straight scribe lines along the entire perimeter of the glasssubstrate 10 a will be each referred to as a “main scribe line DS1”.)Then, four straight subordinate scribe lines DS2 are formed parallel tothe main scribe lines DS1. The subordinate scribe lines DS2 are at adistance of about 0.5 mm to 1 mm from the main scribe lines DS1 and isoutside the glass substrate 10 a.

According to this scribing method, a new scribe line is formed so as tocross a scribe line already formed along a line to be scribed and broken(S1) by swiveling the cutter wheel 20. Thus, the pressure contact forceof the cutter wheel 20 on the mother glass substrate 10 is reduced, andtherefore, a part of the assembled mother glass substrate 10 isprevented from being sunk before the new scribe line crosses the scribeline already formed. This prevents the mother glass substrate 10 frombeing partially chiseled off when the new scribe line crosses the scribeline already formed.

When the advancing direction of the cutter wheel 20 is swiveled at 270degrees as indicated by corners A (or B or C) of FIGS. 8 and 9 and as aresult, the cutter wheel 20 is along the straight line to be scribed andbroken S2 in the lateral direction of the mother glass substrate 10,which is perpendicular to the line to be scribed and broken S1, thecutter wheel 20 is rolled while exerting pressure so as to be in contactwith the mother glass substrate 10 along the line to be scribed andbroken S2. By this operation, a scribe line is formed along the line tobe scribed and broken S2, and avertical crack forming the scribe lineextends in the entire thickness of the mother glass substrate 10.

Then, similarly, the cutter wheel 20 is swiveled at the corner B at 270degrees in a direction perpendicular to the line to be scribed andbroken S2 to draw a circular line having a radius of about 1 mm, withoutbeing separated from the surface of the mother glass substrate 10. As aresult, the cutter wheel 20 is along the line to be scribed and brokenS3. A scribe line is formed along the line to be scribed and broken S3,and a vertical crack forming the scribe line extends in the entirethickness of the mother glass substrate 10. Then, similarly, the cutterwheel 20 is swiveled at the corner C at 270 degrees in a directionperpendicular to the line to be scribed and broken S3 to draw a circularline having a radius of about 1 mm, without being separated from thesurface of the mother glass substrate 10. As a result, the cutter wheel20 is along the line to be scribed and broken S4. A scribe line isformed along the line to be scribed and broken S4, and a vertical crackforming the scribe line extends in the entire thickness of the motherglass substrate 10.

The subordinate scribe lines DS2 are formed in a similar manner at adistance of about 0.5 mm to 1 mm from the main scribe lines DS1 formedby the method shown in FIG. 9. While the subordinate scribe lines DS2are formed, a stress is applied on the surface of the mother glasssubstrate 10 in the horizontal direction which is perpendicular to thescribe line formation direction. As a result, a compressive force actson a surface portion of the vertical crack forming the main scribe linesDS1 already formed. When the compressive force acts on the surfaceportion of the vertical crack forming the main scribe lines DS1, acounter force acts on a bottom portion of the vertical crack in adirection expanding the width of the vertical crack. As a result, thevertical crack extends in the thickness direction of the assembledmother substrate 10 and reaches the bottom surface of the mother glasssubstrate 10.

In this case, the method shown in FIG. 10 is also usable. Main scribelines DS1 are formed. Then, subordinate scribe lines DS2 are formedcontinuously from the main scribe lines DS1 without separating thecutter wheel 20 from the surface of the assembled mother substrate 10,i.e., in one stroke.

The above example uses the one-stroke drawing. The method shown in FIG.11, which illustrates an example in which the one-stroke drawing isrepeated twice, is also usable. In the manner shown in FIGS. 8 through10, main scribe lines DS1 are formed along lines to be scribed andbroken S1 and S2. Then, main scribe lines DS1 areformed a long lines tobe scribed and broken S4 and S3. After this, subordinate scribe linesDS2 are formed.

The above-described substrate scribing and breaking methods are eachpreferably carried out for producing a display panel substrate of aliquid crystal display apparatus. A display panel substrate of a liquidcrystal display apparatus is produced by injecting a liquid crystalmaterial into a gap between a pair of assembled glass substrates. Anexemplary display panel is shown in FIG. 12.

A display panel substrate 50 includes a TFT substrate 51 formed of glassand a CF (color filter) substrate 52 formed of glass, which areassembled together with an appropriate gap interposed therebetween. Inthe gap between the two substrates, a liquid crystal material isenclosed. The TFT substrate 51 includes a plurality of pixel electrodesarranged in a matrix, and a thin film transistor (TFT) connected to eachof the plurality of pixel electrodes. A terminal 51 a provided at an endof a signal line connected to each TFT is located along one peripheralarea of the TFT substrate 51 and also in another peripheral areaperpendicular to the one peripheral area.

The CF substrate 52 includes a color filter (CF). The CF substrate 52 isone size smaller than the TFT substrate 51, and is assembled with theTFT substrate 51 such that the terminals 51 a provided in the TFTsubstrate 51 are exposed.

The TFT substrate 51 and the CF substrate 52 of the display panelsubstrate 50 are respectively produced by scribing and breaking a motherTFT substrate and a mother CF substrate into a substrate of apredetermined size. The mother TFT substrate is a mother glass substrateof the TFT substrate 51, and the mother CF substrate is a mother glasssubstrate of the CF substrate 52. For producing a display panelsubstrate 50, a mother TFT substrate and a mother CF substrate in anassembled state are scribed and broken into a substrate of the size ofthe display panel 50.

With reference to FIGS. 13 and 14, a method for scribing and breaking apair of mother glass substrates assembled together into a plurality ofdisplay panel substrates 50 will be described. FIG. 13 is a plan viewillustrating a method for scribing and breaking a TFT substrate 51 forthe display panel substrate 50 from a mother TFT substrate 510. FIG. 14is a bottom view illustrating a method for scribing and breaking a CFsubstrate 52 for the display panel substrate 50 from a mother CFsubstrate 520.

From the mother TFT substrate 510, for example, six TFT substrates 51 (3rows×2 columns) for the display panel substrates 50 are obtained. In anarea corresponding to each TFT substrate 51, a TFT, a pixel electrode,lines, terminals 51 a and the like are provided. The mother CF substrate520 has the same size as that of the mother TFT substrate 510 andincludes acolor filter (CF) and the like already provided.

Each area of the mother TFT substrate 510 to be a TFT substrate 51 has asealing member 52 b in correspondence with a peripheral portion of theCF substrate 52 which are to be assembled with the TFT substrate 51. Themother TFT substrate 510 and the mother CF substrate 520 are assembledtogether with an appropriate gap interposed therebetween to form theassembled mother substrate 500. Each sealing member 52 b has aninjection opening 51 c for injecting a liquid crystal material intoareas surrounded by the sealing members 52 b between the assembledmother TFT substrate 510 and the mother CF substrate 520. The injectionopenings 52 c provided in the sealing members 52 b are located on thesame side with respect to the areas which are to be TFT substrates 51.

As shown in FIG. 13, the mother TFT substrate 510 is scribed and brokenalong lines to be scribed and broken D10 in the row direction (lateraldirection ) and along lines to be scribed and broken D20 in the columndirection (perpendicular to the lateral direction). Thus, six TFTsubstrates 51 are obtained. As shown in FIG. 14, the mother CF substrate520 is scribed and broken along lines to be scribed and broken D30 inthe lateral direction and along lines to be scribed and broken D40 inthe direction perpendicular to the lateral direction. Thus, six CFsubstrates 52 are obtained. Thus, the assembled mother substrate 500 isscribed and broken into six liquid crystal display panel substrates 50.

More specifically, this is performed as follows. The assembled mothersubstrate 500 is placed with, for example, the mother TFT substrate 510as an upper substrate. Main scribe lines MS and subordinate scribe linesSS described in the above examples are formed in the mother TFTsubstrate 510 using the cutter wheel 20. The mother TFT substrate 510 isbroken along the lines to be scribed and broken D10 and D20, and thussix TFT substrates 51 are obtained.

Then, the assembled mother substrate 500 is inverted to place the motherCF substrate 520 as an upper substrate. Main scribe lines MS andsubordinate scribe lines SS described in the above examples are formedin the mother CF substrate 520 using the cutter wheel 20. The mother CFsubstrate 520 is broken along the lines to be scribed and broken D30 andD40, and thus six CF substrates 52 are obtained. The mother CF substrate520 is scribed and broken such that the terminals provided on theperipheral areas of the mother TFT substrate 510 are exposed. Therefore,the positions of the lines to be scribed and broken D30 and D40 aredifferent from the positions of the lines to be scribed and broken D10and D20, respectively.

In the above examples, methods for scribing and breaking a mother glasssubstrate used for a liquid crystal display panel substrate have beendescribed. The present invention is not limited to this. The presentinvention is applicable to scribing and breaking quartz substrates,sapphire substrates, semiconductor wafers, ceramic substrates and thelike. A substrate scribing and breaking method according to the presentinvention is also applicable to plasma display panels as one type offlat panel display panels, organic EL panels, inorganic EL panels,transmissive projector substrates, reflective projector substrates, andthe like.

INDUSTRIAL APPLICABILITY

According to a substrate scribing and breaking method of the presentinvention, a substrate can be scribed and broken only by forming ascribe line in the substrate. Therefore, an inversion step of invertingthe substrate and a breaking step of breaking the substrate by pressinga break bar on the substrate, which are conventionally necessary, arenot required.

A substrate inversion device and a breaking device are not necessary.Therefore, a substrate can be scribed and broken more efficiently with asimpler structure and a smaller installment area.

1. A substrate scribing and breaking method, comprising the steps of:forming a main scribe line along a line to be scribed and broken of abrittle substrate; and breaking the substrate along the main scribe linewhich has been formed by forming a subordinate scribe line substantiallyparallel to the main scribe line which has been formed, and at adistance from the main scribe line determined so as to generate acompressive force to break the substrate along the main scribe line. 2.A substrate scribing and breaking method according to claim 1, wherein avertical crack having a surface of the substrate as a base portion isformed along the line to be scribed and broken by the formation of themain scribe line; a compressive force is generated on a surface portionof the vertical crack by the formation of the subordinate scribe line,thereby generating a tensile force on a bottom portion of the substrate;and the vertical crack extends to the bottom portion of the substrate tobreak the substrate.
 3. A substrate scribing and breaking methodaccording to claim 1, wherein the subordinate scribe line is formed at adistance of 0.5 mm to 1 mm from the main scribe line.
 4. A substratescribing and breaking method according to claim 1, wherein the mainscribe line is formed of a vertical crack extending over at least 80% ofthe thickness direction of the substrate from the surface of thesubstrate.
 5. A substrate scribing and breaking method according toclaim 1, wherein either the main scribe line or the subordinate scribeline is formed such that a start position or an end position thereof isan appropriate distance away from at least one end of the line to bescribed and broken.
 6. A substrate scribing and breaking methodaccording to claim 1, wherein the main scribe line is formed by adisc-shaped cutter wheel which rolls on the surface of the substrate; acentral portion of an outer circumferential surface of the cutter wheelin a thickness direction thereof projects outward to form a V-shape ofan obtuse angle; and a plurality of protrusions having a predeterminedheight are provided at the obtuse angled portion along the entirecircumference at a predetermined pitch.
 7. A substrate scribing andbreaking method according to claim 6, wherein a forming direction of themain scribe line and a forming direction of the subordinate scribe lineby the cutter wheel are opposite to each other; and the cutter wheelforms the main scribe line and the subordinate scribe line continuouslyin the state of being in contact with the surface of the substrate.
 8. Asubstrate scribing and breaking method according to claim 6, whereinafter at least two main scribe lines are formed by a cutter wheel alongat least two continuous lines to be scribed and broken of the substrate,subordinate scribe lines which are substantially parallel to the atleast two main scribe lines which have been formed are formed by thecutter wheel.
 9. A substrate scribing and breaking method according toclaim 8, wherein the main scribe lines are formed continuously withoutseparating the cutter wheel from of the substrate.
 10. A substratescribing and breaking method according to claim 9, wherein thesubordinate scribe lines are formed continuously without separating thecutter wheel from the surface of the substrate.
 11. A substrate scribingand breaking method according to claim 8, wherein the subordinate scribelines are formed continuously without separating the cutter wheel fromthe surface of the substrate.
 12. A substrate scribing and breakingmethod according to claim 8, wherein the cutter wheel forms one of thescribe lines, then moves on the substrate so as to draw a circular line,and then forms the other of the scribe lines.
 13. A substrate scribingand breaking method according to claim 12, wherein while the cutterwheel moves on the substrate so as to draw a circular line, a pressureacting on the substrate is lower than a pressure acting on the substratewhen each of the scribe lines is formed.
 14. A panel production methodfor scribing and breaking a brittle substrate to produce a plurality ofquadrangular panels continuous in at least one direction, the methodcomprising the steps of: setting four lines to be scribed and broken forthe four-sided panels on the substrate; forming main scribe lines alongthe four lines to be scribed and broken which have been set; andbreaking the substrate along the main scribe lines which have beenformed by forming subordinate scribe lines substantially parallel to themain scribe lines which have been formed, and at a distance from themain scribe lines determined so as to generate a compressive force tobreak the substrate along the respective main scribe lines.
 15. A panelproduction method according to claim 14, wherein the subordinate scribelines are formed at a distance of 0.5-1.0 mm from the respective mainscribe lines.